1. Field of the Invention
The invention relates to a method and a device for determining a statistical measurement parameter for all frequencies of a frequency distribution of signal levels of a test signal registered respectively in several observation intervals.
2. Discussion of the Background
Measuring devices and systems often offer the presentation of signal-level distributions of a signal to be measured against frequency or against time. For this purpose, within a given time raster, it is determined whether in each case a signal level of the signal to be measured is present within the respective signal-level range and at the respective value of the time or frequency raster. In the presence of a signal level of the test signal, a counter associated with the respective signal-level range and the respective value of the time or frequency raster is incremented. At the end of the observation interval, the counter statuses of all counters are read out and supplied to the display device to update the display.
A presentation of this kind is required, for example, for real-time spectrum analyzers, as known, for example from U.S. Pat. No. 5,103,402.
The continuous updating of the display device with the current frequency distribution of the registered signal level of the test signal against time or frequency allows only the presentation of the current frequency distribution—short-term behavior—of the generally stochastic test signal. This is shown in FIGS. 1, 2 and 3 of the drawings, which each present the spectral distribution of a measured signal at different timing points, wherein the frequency of the registered, frequency-dependent signal levels of the test signal corresponds to a specific color or, with regard to FIGS. 1, 2 and 3, to a specific level of grey. FIG. 1 shows the spectral distribution of a band-pass signal in a constantly-active main channel. In FIGS. 2 and 3, in addition to the spectral distribution of the band-pass signal in the constantly-active main channel, the spectral distribution of the band-pass signal is presented respectively in a subsidiary channel active only in the short term. It is evident that the signal information regarding the spectral distribution of the band-pass signal in the subsidiary channel only active in the short-term is presented on the display of the display device only against the time duration of the respectively-active subsidiary channel and is then disadvantageously lost.
Obtaining an item of signal information of the stochastic test signal over a relatively longer time horizon—long-term behavior—wherein signal components active in the short-term are also included and are not lost, cannot be realized with a determination and presentation of the frequency distribution of the signal levels of a test signal of this kind representing the prior art.